Offshore deep drilling method from a floating platform



April 25, 1967 K. M. NICOLSON 3,315,742

OFFSHORE DEEP DRILLING METHOD FROM A FLOATING PLATFORM Original FiledDec. 21, 1956 4 Sheets-Sheet 1 ATTORNEYS April 1967 K. M. NICOLSON 73,315,742

OFFSHORE DEEP DRILLING METHOD FROM A FLOATING PLATFORM Original FiledDec. 21, 1956 4 Sheets-Sheet 2 INVENTOR KINGSLEV M. N/COLSON April 25, 1967 K. M. NICOVLSON OFFSHORE DEEP DRILLING METHOD FROM A FLOATINGPLATFORM Original Filed Dec. 21, 1956 4 Sheets-Sheet 5 25 T /19 INVENTORK/NGSL EV M. N/COLSON ATTORN EYS April 1957 K. M. NICOLSON 3,315,742

OFFSHORE DEEP DRILLING METHOD FROM A FLOATING PLATFORM Original FiledDec. 21, 1956 4 Sheets-Sheet 4 INVENTOR K/NGSLEY M. N/COLSON ATTORNEYSUnited States Patent 3,315,742 OFFSHORE DEEP DRILLING METHOD FROM AFLOATING PLATFORM Kingsley M. Nicolson, Santa Barbara, Calif., assignor,by rnesne assignments, to Chevron Research Company, a corporation ofDelaware Continuation of applications Ser. No. 629,937, Dec. 21, 1956,now Patent No. 3,252,528, dated May 24, 1966, and Ser. No. 631,715, Dec.31, 1956. This application Apr. 20, 1966, Ser. No. 543,887

2 Claims. (Cl. 166.6)

This application is a continuation of my prior application Ser. No.629,937 filed Dec. 21, 1956, now Patent No. 3,252,528, issued May 24,1966, and my prior application Ser. No. 631,715 filed Dec. 31, 1956.

The present invention relates to a method of drilling from a fullyfloating platform. More particularly, the invention relates to a methodof drilling a vertical well bore into the underwater bottom whether ornot the bottom is steeply dipping from a fully floating platform.

It is a particular object of this invention to provide a method ofdrilling a vertical well bore into an underwater bottom from a fullyfloating vessel without requiring a template or other guiding means forspudding in the well bore by suspending a drill string from the deck ofa fully floating vessel with a substantial portion thereof held intension when the lower end thereof including a drill bit and a weightedportion of said drill string touches bottom. Then, with only theweighted portion of the drill string exerting thrust on the drill bitthe drill string is rotated from the working deck of the vessel. Theborehole is spudded in vertically by drilling ahead with the drill bituntil a consolidated rock bed or other competent formation is drilledinto. Then, at least one conductor pipe is cemented in the boreholebefore the drill string is disconnected from the borehole.

Another object of the present invention is to provide a method fordrilling into an underwater bottom from a fully floating platformwithout danger of contaminating the body of water with oil or gasencountered in the well bore by establishing pressure control over theborehole with a well head on bottom before the borehole penetratespotential reservoir formations. od, such well head is set on bottom withall work performed on the working deck of the floating vessel bymaintaining continuous engagement between the underwater bottom and thefloating vessel after the drill string hes been first spudded withouttemplates or other means for guiding the bit into the bottom. In saidpreferred method of carrying out the invention, an assembled conductorpipe is lowered into the vertical borehole formed in the underwaterbottom by the drill bit, but penetration thereinto is limited byassembling a landing flange to the upper end of said pipe before it islowered. The conductor pipe is then cemented in position through a drillstring extending from the deck of the floating vessel into the borehole;said cementing being performed after a guide assembly is lowered on atleast a pair of guide cables so that it slides down along the drillingstring extending downward from the working deck into the borehole. Theguide assembly is latched to the conductor pipe above said landingflange. Following cementing of the conductor pipe and securing of theguide cable assembly to said conductor pipe, the interconnection betweenthe drill string and the floating vessel is broken and the guide cablesslacked to permit cement around said conductor pipe to set withoutvertical force being applied to it through the vessel moving under windand tide action. Pressure control equipment, including at least one blowout preventer assembly is then lowered along the guide cables after theyare again drawn taut between the well head and the floating vessel. Saidpressure control equipment In carrying out the methice is desirablycoupled to the top of the conductor pipe by a safety joint or otherquick-connect joint that requires less than one full rotation of thepressure control means, guide lines or said conductor pipe.

In this connection an individually significant object of the inventionentails the detachable connecting of a wellhead assembly to cemented-inconduit means in response to axial convergence of, and relative rotationbetween, the wellhead assembly and the conduit means vis-a-vis a safetyjoint. This detachable connection enables the wellhead assembly to beselectively detached from the conduit means and raised in slidableengagement with flexible guide means toward support means such as afloating vessel. This connection of the wellhead assembly with theconduit means prevents upward movement of the wellhead assembly andrelative rotary movement between the wellhead assembly and the conduitmeans and also provides a drill pipe passageway in sealed communicationwith the interior of the conduit means. This drill pipe passageway iscontrolled, by means of the blowout preventer, from the support means sothat the passageway, from the support means, may be selectively closedoff or opened.

In the drilling of well bores to explore for oil, gas and the likethrough deep waters, it is necessary either to build a platformextending from the ocean bottom to a level well above the water surfaceor to drill from a floating platform. It is of course uneconomical tobuild large fixed platforms unless there is a high probability offinding oil. Accordingly, it is desirable to be able to drill a wellbore from a mobile platform such as a floating platform. The greatermobility of a fully floating platform makes this type of drilling moreattractive than platforms that have a floating foundation partlysubmerged by vertical anchors. While such restrained floating platformsprovide easier drilling conditions, the cost of vertical anchors makestheir use economically unattractive.

While in general it has been proposed to anchor a vessel over a drillingsite and then drill into the underwater bottom with conventional rotaryequipment, such underwater bottoms are seldom level and hard so thatadequate pressure control equipment can be set directly on bottom. Thefunction of such pressure control equipment is to maintain hydrostaticpressure in the well bore that will always be greater than that of anygas or oil encountered therein. Loss of such pressure control is knownas a blow out. The problem of blow outs is of course a serious one fromthe standpoint of explosion and fire hazards in land operations. It iseven more serious in offshore operations, such as those along theCalifornia coast, where any release of oil or gas could contaminate theocean so that marine life is destroyed and the adjacent resort beachesruined. Accordingly, it is considered imperative that adequate andcomplete well head control equipment he established before drilling ispermitted in an underwater bottom where contamination of the water ispossible.

It has been suggested heretofore that well head controls be located onthe working deck of the drilling vessel to give easy access formaintenance and to assure its recovery when drilling is completed. Inthis system, a conductor pipe runs from the well bore up to the controlequipment located on the deck of the surface vessel. This of courserequires that the conductor pipe be flexible enough to permit lateraland vertical movement of the surface vessel while drilling. One seriousproblem in using pressure controls at the deck is that the wind and tideforces on the vessel can put an undue strain on the conductor pipe. Suchstrain, of course, makes the conductor pipe more susceptible to damagethat can result in complete loss of well head control. For thesereasons, it is desirable to position the well head control esuipment nthe bottom. However, the pressure control equipment 5 quite expensiveand therefore it is desirable that it be :ossible to retrieve it afterthe well is drilled.

While it has been suggested heretofore that well head .ontrol equipmentbe placed on bottom, the method of nitiating, or spudding-in theborehole, landing of conluctor pipe and control equipment, as well asretrieving his equipment as practiced heretofore frequently required heaid of a human diver, or other auxiliary equipment 1ot forming part ofthe normal drilling equipment. The :ost of diver service, in addition torig time (i.e., rental :harges on drilling equipment, drill crew wages,etc.), nakes these operations unusually expensive. In general, :he costof a diver service alone may run as high as $800 to $1,000 per day.Additionally, the time that a diver can operate, even in shallow water,is greatly limited by human, physical endurance. In deep waters, it isnot feasible to use a diver even if one is required. Additionally, inwater bottoms having a thick bed of unconsolidated sediments, diverservice cannot be used without difficulty.

For the foregoing reasons, it is necessary and desirable that there beprovided a system for drilling a vertical borehole into an underwaterbottom irrespective of its slope or hardness and to a depth so that aconductor pipe can be set and cemented in a competent formation with atleast an upper portion thereof extending above bottom to receive wellhead or pressure control equipment. (In this sense, competent means anearth formation, such as a consolidated shale bed, having sufficientcompaction to give it strength and being impermeable so that the pipecan be bonded to it with cement.)

In accordance with a preferred method of carrying out the presentinvention, a drill bit is assembled on the lower end of a conductor pipehaving a predetermined weight. The drill bit and conductor pipe are thenconnected to a drill-string through a vertically-reciprocableconnection; said drill string in turn is rotated by a gimbaled rotarytable positioned below a supporting drill derrick mounted on the workingdeck of the fully floating platform. The vertically-movable connectionpermits the entire string to hang freely as a pendulum below the vesselso that even in deep waters only the predetermined weight of theconductor pipe is imposed on the drill bit when the bit first touchesbottom. Then without further guiding thereof, the drill bit is rotatedwith only said predetermined weight thereon and with a substantialportion of the drill string in tension during spudding-in. By suchrotation and holding said drill string in tension above the weightedsection the bit and drill string is maintained vertical even on verysteeply dipping bottoms. Drilling then continues until the borehole isdeep enough to receive the full length of the conductor pipe. A landingflange otherwise serving as a feeler for bottom indicates when theconductor pipe has been drilled deep enough into the bottom. Desirably,this depth is preselected so the conductor pipe will be sufficientlylong to assure its penetration into a competent formation. After thelanding flange has engaged bottom with the conductor pipe attachedthereto and extending into the borehole, cement is supplied to theannual space between the conductor pipe and the borehole whileconnection between the drill string and borehole is maintained.Desirably, this is done without removal of the drill string from thewell bore. Alternatively, the conductor or surface pipe may be cementedin the borehole using a cement string guided into the landed conductorpipe through a guide assembly lowered on at least a pair of cables alongthe drill string while said drill string is still in the well bore. Ineither method of cementing, said guide assembly is lowered to slide downalong the drill string while said string is still in the borehole and toestablish a continuity of connection between the deck of the drillingvessel and the conductor pipe in the borehole before cement is injected.This 4 continuity of interconnection between vessel and borehole justprior to the cementing operation is particularly essential to eliminatehuman diver service.

When the guide assembly, which desirably includes an enlarged funnelused to guide well head pressure control equipment into engagement withthe conductor pipe, has been landed and interconnected, the drill stringis disconnected from the borehole immediately above the landing flange.Then, the guide cables are released so that cement between the conductorpipe and the borehole may set without danger of the conductor pipe beingpulled up by the cables due to action of wave and tide forces on thedrilling vessel. Said conductor pipe not only serves to prevent slutfingof the underwater sediments into the well bore, but also provides a firmvertical anchor for blow out prevention equipment connected thereto asdrilling proceeds below the cemented section of the conductor pipe downinto potential oil and gas-bearing formations.

After said conductor pipe has been cemented in the borehole inaccordance with the invention, drilling proceeds to a greater depththrough blow out prevention equipment, and other well head controlequipment, coupled directly to the conductor pipe. Such well headequipment is assembled to the conductor pipe by again tightening theguide cables and lowering it along them. Final assembly of said wellhead equipment to the con ductor pipe is desirably made through aquick-connect joint, otherwise known as a safety joint, which permits afluid-tight connection without requiring significant rotation of theguide cables, blow out preventer, drilling head or other equipment thatguidably slides down along the cables. In particular, this equipment isnot rotated through as much as a full revolution so that the controlhydraulic lines and the drilling fluid return lines will not becometwisted during assembly. Thus, the hydraulic control means for remotelyoperating the well head equipment from the vessels deck can be connectedprior to lowering of said equipment along the guide cables. At the sametime, said guide cables are held nearly straight and vertical betweenthe borehole and the drilling vessel. After assembly of said well headequipment and the drilling head, drilling proceeds by guiding a drillbit and the drill string along the guide cables and into the drillinghead assembly and the borehole.

The drilling operation then proceeds under full pressure control of thewell bore. This, of course, includes the use of drilling fluid thatreturns to the working deck through a mud return line connected to theborehole at a point intermediate the biow out prevention equipment andthe drilling head. Upon completion of drilling, it is desirable toabandon said borehole, but prevent any possible seepage or other escapeof oil or gas by setting a cement plug in the well bore of sufficientlength to bond both to the uncased portion of the borehole and at leastpart of the cased section of the borehole. Such abandonment will ofcourse occur where it is decided that production cannot be eS-tablished, or for other reasons, it is not desired to complete aproducing well through this particular borehole. After cement has beenspotted in the hole, the well head control equipment is disconnectedthrough said safety joint, or other quick-connect joint, and then liftedby a drill string to the work deck of the drilling vessel. The guidecable assembly, then in turn, is retrieved either by increasing tensionon said guide cables to sever a breakable link between the cementedconductor pipe or landing flange and the guide assembly, or byinterconnecting said guide assembly with a portion of a drill string tolift the guide assembly and sever the breakable link to the cementedconductor pipe.

In accordance with another method of carrying out the present invention,the conductor pipe is drilled into the underwater bottom by a concentricdrill string including a plurality of drill collars directly above thebit but below the section of drill string held in tension from the workdeck so that the desired load is applied to the bit when it touchesbottom. In accordance with the invention, no other guiding means is usedto start said well bore in the bottom. The conductor pipe then islowered directly behind said drill string, which opens a pilot hole andthen underreams it to expand the hole to a diameter large enough to letthe conductor pipe pass into the borehole. The landing flange assembledto said pipe limits its depth of penetration; in this method the landingflange and guide assembly are assembled to the conductor pipe and thecomplete unit is lowered from the deck on the guide cables while saiddrill string is still in the well bore maintaining continuity ofconnection between the borehole and the deck.

Further objects and advantages of the present invention, both in themethod of its application to drill a vertical hole into bottom withouttemplates or other guiding means while drilling from a floating vesseland the method of remotely establishing said well head control on bottomfrom the working deck of a drilling vessel will become apparent from thefollowing detailed description of the method and its mode of operationas illustrated by the various forms of apparatus shown in theaccompanying drawings which form an integral part of the presentspecification.

FIG. 1 is a schematic elevation view of one form of apparatus fordrilling into an underwater bottom from a fully floating vessel inaccordance with the method of the present invention;

FIG. 2 is a vertical section of the lower end of the drill stringillustrated in FIG. 1 after the landing flange has been seated on bottomand cementing of the conductor pipe has begun;

FIG. 3 illustrates the lower end of a conductor pipe, including a drillbit attached thereto, at the completion of cementing between the wellbore and the conductor p p FIG. 4 is a vertical view, partly in section,illustrating the positioning of the guide assembly after it slides downthe drill string and engages the conductor pipe in the borehole with thedrill string still connected to the well bore;

FIG. 5 is a vertical view of the underwater well head or pressurecontrol equipment being lowered along the guide cables to engage thesafety joint that couples the conductor pipe to said wellhead equipment;

FIG. 6 illustrates an alternative method for opening a borehole into theunderwater bottom with an independent drill string wherein the conductorpipe and guide assembly are preassembled concentric with said drillstring for lowering therealong into the borehole as a unit and said unitis held suspended below the drilling vessel on guide cables that lowerit to bottom;

FIG. 7 illustrates setting of another surface pipe to be cemented withinthe conductor pipe in the method illustrated in FIG. 6;

FIG. 8 illustrates a preferred method of severing the upper end ofsurface pipe as seen in FIGS. 6 and 7 to permit recovery of the completesafety joint with the well head control equipment when the well bore isto be abandoned.

Referring now to the drawings and in particular FIG. 1, there isillustrated a method of drilling a vertical well bore into an underwaterbottom that may be steeply dipping from a fully floating vessel 10. As afirst step, vessel 10 is suitably positioned and anchored over the drillsite as indicated schematically by anchor lines 11. After the vessel hasbeen positioned on the drill site, there is suspended through a centralwell 12 formed in vessel 10 to a drill string 14 that includes anassembled section of conductor pipe 13. In the arrangement of FIG. 1,conductor pipe 13 is to be cemented in hole 15, but is an integral partof drill string 14- that also includes drill bit 17, safety joint 19 andan upwardly extending, reduced diameter section 21 formed of a string ofdrill pipe. Conductor pipe 13 is assembled to a predetermined lengthdepending on the depth of the unconsolidated sediments, identifiedgenerally as 23, and the depth needed to be drilled before a competentformation is found in the solid rock 25. Conductor pipe 13 is likewiseselected to have a predetermined weight that will act as the only weighton bit 17 when the bit first touches bottom and irrespective of thedepth of water between the vessel and bottom. In open water, vessel 10will be subjected to periodic rise and fall, as well as pitching androlling, due to wave and tide action. For this reason, the string ofdrill pipe 21 includes as an integral part thereof, a splined or slidingsleeve connection 43 that assures that the bit will rest on bottom withonly the desired load thereon. In the arrangement of FIG. 1, drillstring 14, including conductor pipe 13, is then supported by vessel 19through a conventional derrick 27 that includes hook 29, travellingblock 31, cable 33 and draw works 35. In drilling, it is to be notedthat templates, pipes or other guide means are not required inaccordance with invention to start and drill borehole 15 vertically intoa dipping bottom where the upper end 21 of drill string 14 is held intension so that the entire string hangs as a compound pendulum belowrotary table 39. Drill bit 17 is rotated on bottom by rotary table 39driven by any suitable power source such as motor 41. Preferably, motor41 is a rotary hydraulic motor so that the motor can be driven throughflexible hydraulic lines with the motor supported on the gimbaledbearings of rotary table 39. Rotary table 39 is so mounted to permit itto remain level when the vessel pitches and rolls.

For the purpose of indicating the condition when conductor pipe 13 hasbeen drilled to the desired depth, and to limit its penetration alanding flange 45, formed as either a four-armed spider, or as arelatively flat plate of somewhat enlarged diameter, is clamped to thetop end of conductor pipe 13. Thus, when conductor pipe 13 has beendrilled to the desired depth, the driller will immediately be notifiedby an increase in torque at the rotary table and/or by a decrease in theweight supported by derrick 27 due to part of the weight of uppersection 21 of drill string 14 being supported on flange 45. The drillingof the conductor pipe is desirably accomplished by using sea water as adrilling fluid. In the present arrangement this is illustrated by intakepipe 47 being interconnected to a pump 49 and to drill string 14 throughhose 51 and swivel 53. During drilling-in with sea water, there is ofcourse no return of the cuttings to vessel 10.

In the arrangement shown in FIGS. 1 to 3, drill bit 17 has an enlargeddiameter and includes a core wiper arm 54 in the center of the bit thatkeeps the hole open thrdugh the center of conductor pipe 13.

When the conductor pipe has been drilled to suflicient depth to enter acompetent formation, landing flange 45 touches bottom as seen in FIG. 2.The hole is then conditioned by continued circulation of sea water sothat the hole is flushed of debris. After conditioning of thehole,cement is supplied by switching connections of valve 57 to pump cementfrom the mixing tank 59 through mud pump 49 and into drill pipe 14through swivel 53 (FIG. 1). As best seen in FIG. 2, cement is clearedfrom conductor pipe 13 by dropping a ball 61 through a side-opening portor kelly cock 63 connected directly below swivel 53. When ball 61 seatson the top of cement chaser 65, pump pressure, as indicated by meter 50,will be increased to release chaser 65 from its seat in coupling 67 inthe drill string lying directly above safety joint 19. Cement chaser 65then cleans cement from the lower end of the conductor pipe as shown inFIG. 3. Core wiper 54 stops the downward travel of cement chaser 65 andprevents back flow of cement 69 from well bore 15 into conductor pipe13. Desirably, enough cement is used so that substantially 7 ;he entirelength of conductor pipe 13 is cemented in the 101e, but not enough isused so that cement balls up over the top of landing flange 45.

After the cement is placed around the conductor pipe, a guide assembly,identified generally as 71, is lowered on a pair of guide cablesidentified as 73. As seen in FIG. 1, guide assembly 71, initially hangsin the well 12 of vessel 10 below the rotary table. Guide assembly 71includes a tubular member or bucket element 75 that gives the assemblysubstantial weight. The assembly is free to slide down along drill pipe21 and over the outer portion of safety joint 19 when the guide linesare slacked from cable drums 76 on the vessel. When landed adjacent to,or on top of, landing flange 45, as in FIGS. 4 and 5, bucket member 75is latched to the lower or stationary portion 77 of safety joint 19 by apair of latch members 78 that engage groove 72 in lower member 77.Alternatively, bucket or weight member 75 may latch directly toconductor pipe 13 or to landing flange 45 if so desired. The function oflatches 78 is to connect guide assembly 71 to the upper end of conductorpipe 13 by shearable links, such as pins 8i Pins 30 are breakable by anupward pull on bucket 75 of a predetermined magnitude that rotateslatches 78 about pivot pins 82. The respective pins 32 pass throughcorresponding elongated openings formed through the pivoted end portionsof the latch members 78. These openings are disposed to permit thelatches to slide on the pins toward and away from the latching positionas well as to pivot around the pins. A respective spring biases eachlatch to its latching position. Thus when the bucket member 75 islowered over the portion 77 of the safety joint the radially disposedprojections on the latter displaces the latch members outwardly topermit the bucket assembly to clear such projections until the latchmembers are in alignment with the groove 72. When the bucket assemblyreaches this position the biasing springs force the ends of the latchmembers into engagement with the groove. The groove-engaging end portionof the latch members are notched to form a surface complementary to thatof the upper radially disposed surface of the groove. This provides asecure engagement between the groove and the latches and prevents thelatch members from being displaced radially by normal working stresses,as indicated in FIG. 5. As shown in FIGS. 4 and 5, guide assembly 71 hasa pair of arms 79 that extend radially outward from the center line ofthe borehole to anchor the lower ends of guide cables 73.

As best seen in FIG. 1, guide cable 73 are normally maintained tautbetween bottom and floating vessel 10 by a weight 81 hung on sheaveassembly 83 below cable drum 76. After bucket 75 of guide assembly 71has been latched to conductor pipe 13 preferably, the upper portion orbarrel section 85 of safety joint 19 is disconnected by retracting thelocking sleeve 86 (shown in FIG. 2) from locking grooves in thestationary portion 77 (shown in FIG. so that the string of drill pipe 21forming the upper section of drill string 14 can be raised and racked onthe drill deck, ready for further drilling through the lower end of thecemented casing 13. The operation of this safety joint is described morefully in my Patent No. 2,950,929.

From the prior discussion and from the drawings, and especially FIG. 5,it is obvious that this safety joint enables the wellhead assemblyincluding the blow out preventer 99 to be detachably connected withconduit means 88 and 13 in response to axial convergence and limitedrelative rotation between the wellhead assembly, which includes safetyjoint barrel 85, and the aforesaid conduit means which terminates in thesafety joint mandrel 77.

As will be appreciated, the flexible guide cables 73 enable this limitedrelative rotation to take place.

This mode of connection is the obvious mode of operation involved in thecoupling of the safety joint mandrel 77 to the safety joint barrel 85,in view of the prior description of the invention and the structureshown on FIG. 5, which structure is well known in the art.

Those conversant with the art will also recognize from the safety jointstructure shown on FIG. 5 that the connection of the mandrel 77 with thebarrel will prevent upward movement of the wellhead assembly, includingthe barrel 35 and blowout preventer 99, and will also prevent rotarymovement between this wellhead assembly and the cemented-in conduitmeans 88 and 13.

With the operation of the safety joint having been reviewed, thepreviously interrupted description of the submerged wellhead preparationmay now be resumed.

At this time, in accordance with the preferred embodiment of the presentinvention, guide cables 73 are slacked off so that conductor pipe 13 isleft standing free in the well bore and supported on flange 45 while thecement sets. Thus, cement 69 is not worked by the conductor pipe orpulled up by the guide cables while it sets. Alternatively the drillstring may remain connected to the conductor pipe after the cement isplaced around the latter, the sliding connection 43 functioning toisolate the vertical motion of the vessel 10 from the conductor casingwhile the cement sets.

After cement 69 has set, conductor pipe 13 is securely anchored in acompetent formation along the well bore. Drilling then proceeds throughthe conductor pipe, in a manner to be explained hereinafter, by drillingup ball 61 and the part of the cement at the bottom of the borehole. Inaccordance with the method illustrated by apparatus shown in FIGS. 1 to5 inclusive, the well head or pressure control equipment is coupleddirectly to conductor pipe 13 through safety joint 19 heretofore formingpart of the drilling string. In said method, as illustrated in FIG. 5,the barrel 85, including locking sleeve 86 illustrated in FIG. 2, ofsafety joint 19 are assembled below a well head assembly, identifiedgenerally as 87. While the well head or pressure control assembly willvary in accordance with the pressure conditions that are expected to bemet in drilling ahead, in the present arrangement it comprises a pair ofgate-type blow out preventers (hereinafter called BOPs) 89 and 91assembled in series to the upper end of safety joint barrel 85. In apreferred form of apparatus for carrying out the invention, lower BOP 89includes a pair of shearing rams constructed in accordance with myPatent No. 2,919,111, filed December 30, 1955. As disclosed in saidpatent, the opposite sides of the pipeengaging rams that normallyencircle a section of drill pipe, similar to those in BOP 91, as seen inFIG. 5, are provided with shearing bars that override one another. Thepurpose of these shearing rams is to provide a system, such that ifstorm or other hazardous operating conditions require, the drill pipe inthe borehole can be cut off at the well head without requiring eachsection of the entire string to be raised, uncoupled and racked beforethe hole can be abandoned. Such action is of course drastic in that theentire length of drill pipe would need to be recovered if the hole is tobe used again; such apparatus provides a method for leaving the hole,but at the same time maintains full control of well pressures whileabandoning the borehole under emergency conditions.

Upper blow out preventer 91 is of conventional design and may eithercompletely close off the well bore, or grasp the sides of the drill pipewhen the opposite rams 9t and 92 are actuated through hydraulic lines93. Similar hydraulic lines 94 permit control of BOP 89 from the deck ofvessel 10.

Immediately below blow out preventer 89, there is provided a mud fill-upline connection identified generally as 95. A valve 97, hydraulicallyoperable through line 96 permits drilling fluid to be added underpressure to the well bore when drill pipe is out of the borehole. Foradditional safety in the operation of well head assembly 87, there isincluded another pressure controlled full hole blow out preventer 99connected directly to and above BOP 91. BOP 99 is operable through line100. By this arrangement of BOPs 99, 89 and 91, it is possible to holdcontrol of the well even if control of one of said BOPs is lost byaccident.

Above BOP 99, there is positioned a drilling head 101 whose function isto maintain a hydrauic seal around the rotating drill pipe; said drillpipe not only rotates but also reciprocates therein due to rise and fallof vessel due to waves. Drilling head 101 likewise places a backpressure on drilling fluid returning from the borehole around theoutside of drill pipe 21 and forces said drilling fluid to flow back tothe deck of vessel 10 by way of mud return line 103. Control of the backpressure on drilling fluid returns is by a packing locked by hyadrulicpressure applied through line 104. The returned drilling fluid of coursecontains the cuttings from the formation being drilled. These can betested by conventional gas and Chip analysis methods. As indicated,return mud line 103 is connected through a side-opening flange member105 positioned directly below drilling head 101.

As indicated above, various combinations of blow out preventionequipment, either of the full hole, or drill pipe engaging types may beassembled between the top of the cemented conductor pipe and thedrilling head. However, desirably this entire assembly is made on thedeck of vessel 10 or in the well 12 through the vessel and then loweredon a section of drill pipe 21A, as shown in FIG. 5. In positioning thisequipment through center well 12 of the driling vessel an upper andlower pair of guide arms, indicated as 107 and 109 respectively,slidably engage the pair of guide cables 73. A spearing section of drillpipe 21A, preferably having a bull nose portion 111, extends downwardlythrough the entire well head assembly 87 and below safety joint barrel85. In lowering assembly 87, rams 90 and 92 of upper BOP 91 are closedaround a recessed collar portion 102 positioned a fixed distance abovebull nose 111.

As indicated schematically in FIG. 5, bull nose 111 is guided alongcables 73 by guide arms 107, 109 so that even with ship 10 rising andfalling in the water, the well head assembly and in particular barrel 85of safety joint 19 is guided over mandrel 77 of safety joint 19 byfunnel 113 above bucket member 75. For this purpose, a funnelarrangement 113 has a suitably enlarged diameter'that is formed as anintegral part of guide assembly 71. Thus, with guide cables 73 againdrawn taut, well head assemby 87 slides down said guide cables whilelowered by derrick 27. Through the latching of barrel 85 to mandrel 77of safety joint, or quick connect unit, 19 a positive connection is madebetween the well head assembly and the conductor pipe.

As suggested by FIG. 5, each of the control hoses 93, 94, 95, 96, 100,103 and 104 is connected to the well head assembly before it is loweredto engage the conductor pipe. Preferably, this is also accomplished ondeck, although it can be performed directly below the surface of thewater as in well 12 in vessel 10. These control lines preferably passover the side of the vessel 10 and are wound on a reel assembly. Intheir assembly, the entire bundle is passed over the side and the lowerend fished up through center well 12 of vessel 10. Thus, the outer endsof each of the hoses may be attached while the assembly is in the wellor on the working deck and above water; then, the entire assembly islowered along guide cable 73. After the well head assembly is connectedto the conductor pipe in the manner explained hereinbefore, the rams 90and 92 of BOP 91-areopened to release the drill pipe 21A, and thelatter, together with the attached bull nose portion 111, is raised fromthe assembly and returned aboard the drilling vessel.

Drilling may now proceed to any desired depth with full pressure controlover the well bore and with the well head located on the ocean bottom sothat if required, for

safety of vessel or personnel, the well can be abandoned temporarilywithout loss of pressure control in the well. In such abandonmentprocedure, the hoses can be severed and the guide line 73 dropped withonly buoys to mark their location at the ocean surface, and if need be,the drill pipe can be severed in the hole without danger ofcontaminating the ocean waters or the adjacent beaches.

As best indicated in FIG. 5, after the well head is assembled, the drillbit is assisted in entering and leaving the well head assembly byanother funnel member 117 that is directly connected to upper guide arm107. Funnel 117 and guide arm 107 are secured directly to drilling head101. Additionally, the bit is guided by a collar arrangement, otherwisecalled a bit guide, that surrounds the drill pipe directly above thebit; said bit guide includes a pair of arms that engage and slide downalong the guide cables to assist the bit in entering the drilling head.

There is illustrated in FIG. 6 another method of establishing wellpressure control after drilling into the underwater bottom by the methodof the present invention. In this embodiment, a hole opener bitarrangement, identified generally as 121, including a pilot bit 123first touches and penetrates the'bottom to open a relatively small hole.Pilot bit 123 is then followed by an underrearner bit 125. In thissystem of drilling in, a desired length of conductor pipe or casing 127is supported below the ships center Well 12 and is assembled to alanding flange assembly 129 and guide assembly 131, so that the entireassembly can be hung on guide cables 73 by arms 133. As shown in FIG. 6,the guide assembly 131 is secured by links 135 directly to landingflange assembly 129, rather than to the conductor pipe, but in thepresent case flange assembly 129 is welded to conductor pipe 127. Theconductor pipe 127, landing flange assembly 129, and guide assembly 131are all assembled below the rotary table prior to spudding in of thewell, and as shown drill string 122 is lowered through conductor pipe127.

After the borehole has been opened and underreamed to a suflicient depthand diameter to receive the preassembled length of conductor pipe 127,said conductor pipe and guide assembly 131 are lowered along the drillstring in the same manner as guide assembly 71 is lowered along drillstring 21 in the arrangement of FIGS. 1, 4 and 5. With the conductorpipe set in the well bore and guide assembly 131 connected to the vesselthrough cables 73, drill string 122 can be withdrawn to substitute acement shoe for bit 121. However, if desired said drill string caninclude a cement shoe 'so that the drill need not be removed from theborehole to cement conductor pipe 127 in the borehole. The conductorpipe is cemented in the well bore in much the same manner as illustratedin FIG. 2. Where a cement tool is used, it is guided into the conductorpipe by a bit guide sliding down the guide cables 73 and into theborehole by funnel 137. Sufiicient cement is of course added to fill theannular space between the side of the well bore and the conductor pipe.Desirably, only enough cement is added at this stage so that the cementdoes not rise to the top of the conductor pipe as shown in FIG. 7. Aswill be explained later in connection with FIG. 7, this permits ports141 in landing flange assembly 129 to act as cement openings whenangther pipe or liner 143 is cemented within conductor pipe Inaccordance with the method disclosed in the arrangement of FIGS. 6, 7and 8, the well bore is drilled to a greater depth before setting ofblow out preventers or other well head control means. Such an operationis usually undertaken when a knowledge of the geology of the underwaterbottom indicates that gas and oil under pressure will not be encounteredduring the first few hundred feet of drilling. Accordingly, drilling canproceed through the bottom of cemented conductor pipe 127, after thatpipe is set to prevent debris or unconsolidated sediments from sloughinginto the borehole. In practice, the conductor pipe will be set to adepth of about 50 to 75 feet, the depth of surface casing 143 may be ofthe order of 300 feet, and usually is deep enough so that a competentformation, such as a thick bed of impervious shale or other non-porousrock is encountered by the borehole. By going deeper into the earthbefore cementing surface casing 143, a much greater depth and higherpressures can be withstood by the pressure control equipment Withoutdanger of high pressure oil and gas accumulations blowing out.

There is illustrated in FIG. 7 a preferred method of assembling the blowout prevention equipment, as well as the preferred method of cementingthe surface casing into the deepened well bore. As there shown, surfacecasing 143 extends downwardly to about 300 feet and is run into the wellthrough conductor pipe 127. The upper end of surface pipe 143 preferablyincludes a cement sleeve 145 that extends axially along the upper end ofsurface casing 143. Sleeve 145 is tapered at its lower end 147 so thatit can be sealed by welding to the outer surface of the surface casing.The upper end of sleeve 14S frictionally engages coupling 149 on themandrel 277 of a safety joint 213. The purpose of cement sleeve 1 55, asbest seen in FIG. 7 is to permit the upper end of surface casing 143 tobe cemented into conductor pipe 127, but to leave an annular space 15)that will not be filled with cement.

As further distinguished from the arrangement of FIGS. 4 and 5, aconically tapered portion of mandrel 277 of safety joint 21) seatswithin a conical section 157 of landing flange assembly 129 that servesas a tubing hanger for surface casing 143. In this way, casing 143 issupported throughout its length until it is cemented into the well boreas illustrated in FIG. 7. In the present embodiment, surface pipe 143 ishung in the well bore on safety joint 21% so that the drill stringthereabove can be disconnected after cement has been set through cementshoe 151 at the lower end of pipe 143. "Pipe 143 is guided into the holeby bit guide 221 that will pass the barrel of safety joint 219 to let itrest above guide arms 133 of guide assembly 131. The upper end ofmandrel 277 is sealed against cement by O-rings 161.

Deep drilling is then possible under full pressure control by landingwell head equipment, identical to that of FIGURE 5, on safety joint 219.This couples the blow out preventers and the drilling head to axiallycemented section of surface casing 143. After the desired depth isdrilled, it may be desirable to abandon the well bore. When it isdesired to leave the well, the surface casing will normally be left inthe well bore with cement spotted therein to prevent any possible blowout from the borehole. Then, the entire assembly of well head equipmentis recovered by severing the upper portion of surface casing 143opposite annular section 15% between cement sleeve 145 and the casing.FIGURE 8 represents a preferred manner of severing casing 143 with ashaped explosive charge. The tubing can also be cut by a milling cutterrun into the casing. Upon severance of the upper end of casing 143, thecomplete safety joint 219 and the well head equipment secured theretocan be withdrawn from within landing flange assembly 129. After releaseof the well head equipment, the guide assembly 131 can also be recoveredin much the same manner as that illustrated in FIG- URES 4 and 5. Thatis, the lines or cables 73 can be tightened to sever pins 163 that holdlinks 135 to landing flange assembly 129. Desirably, guide assembly 131is pulled free from landing flange assembly 129 by a special tool runinto guide assembly 131 on a drill string. As indicated in FIGURE 3,weight or bucket element 165 of the guide assembly has a pair of diametrically opposed J-slots 167 formed in its upper, inner surface. Slots167 can be engaged by the lifting tool so that the drill derrick hoistcan apply the necessary force to shear pins 163. In this way, only thecemented casing and landing flange assembly 129 are left on bottom.

Where only a single pipe is cemented in the well bore,

as in the apparatus shown in FIGURES 1 to 5, the conductor pipe alsodesirably has a cement sleeve surrounding its upper end. This is bestseen in FIGURE 5, where the details of the connection between safetyjoint 19 and conductor pipe 13 are shown in vertical section. In thisarrangement sleeve 88 is welded to conductor 13 at its lower end andslips over the lower coupling end of mandrel 77 of safety joint 19. Inthis embodiment, severance of conductor 13 within the cement sleeveallows recovery of landing plate 45 as well as safety joint 19.

In the foregoing detailed description of two forms of apparatus forcarrying out the method of the present invention, it will be apparentthat various modifications and changes can be made in both said methodand the apipaartus without departing from the present invention.Accordingly, all such modifications and changes falling within the scopeof the appended claims are intended to be included therein.

I claim:

1. A method of preparing a well in a formation underwater for wellworking operations, said method comprising:

lowering conduit means from support means downwardly through the waterand positioning said c-onduit means at least partially within an openingextending downwardly into an underwater formation with an upper end ofsaid conduit means submerged beneath water;

from said support means, conveying cementitious material to a zoneexterior of said conduit means and within said opening;

sealingly cementing at least a portion of said conduit means to wallmeans of the opening in said formation;

guiding a well head assembly having a well apparatus passagewayextending therethrough from said support means toward said conduit meansby lowering said well head assembly in slidable engagement with flexibleguide means extending downwardly from said support means;

prior to said guiding of said well head assembly, providing saidflexible guide means supported by said support means and extending tothe general vicinity of said submerged upper end of said conduit means,with said upper end of said conduit means being exposed;

axially converging and engaging portions of said well head assembly andsaid exposed upper end of said conduit means; interconnecting said wellhead assembly with said upper end of said conduit means and establishingsaid Well apparatus passageway in sealed communication with the interiorof said conduit means;

mechanically and detachably interlocking said interconnected well headassembly and upper end of said conduit means to mechanically preventdisconnection of said well head assembly and said upper end of saidconduit means; mechanically and selectively maintaining saidinterlocking of said well head assembly with said upper end of saidconduit means, with said interlocking being selectively maintainableuntil said well head assembly is to be disconnected from said end ofsaid conduit means and raised in slidable engagement with said flexibleguide means; and

controlling the well apparatus passageway of said well head assemblyfrom said support means whereby said well apparatus passageway may beselectively closed off or opened.

2. The method of preparing a well in a formation underwater fordrilling, said method comprising:

suspending a landing assembly, comprising a landing base supported onconduit means, on a drill string extending downwardly from supportmeans, with the conduit means having a bit on its lower end and acoupling portion on its upper end detachably connecting said conduitmeans to said drill string for unitary rotary movement therewith,

lowering said landing base, conduit means and bit by lowering said drillstring from said support means,

forming an opening extending downwardly into a bottom formation bydrilling a portion of said conduit means into a bottom formation bymeans of said drill string extending from said support means, limitingthe extent to which said conduit means is drilled into said bottomformation by engagement between said landing base and said bottomformation with said conduit means being secured against downwardmovement relative to said landing base,

from said support means, conveying cementitious material to a zoneexterior of said conduit means and within said opening,

sealingly cementing at least a portion of said conduit means to wallmeans of the opening extending into said bottom formation,

guiding a well head assembly having a well apparatus passagewayextending therethrough from said support means toward said conduit meansby lowering said well head assembly in slidable engagement with flexibleguide means extending downwardly from said support means,

prior to said guiding of said well head assembly, providing saidflexible guide means supported by said support means and extending tothe general vicinity of said submerged upper end of said conduit means,and disconnecting said drill string from said coupling portion andraising said drill string to said support means to leave said couplingportion of said conduit means exposed,

axially converging and engaging portions of said well head assembly andsaid coupling portion of said conduit means,

moving said well head assembly downwardly and inducing relative rotationbetween said engaged well head assembly and coupling portion of saidconduit means to interconnect said well assembly with said couplingportion of said conduit means and establish said drill pipe passagewayin sealed communication with the interior of said conduit means,

mechanically and detachably interlocking said interconnected well headassembly and said coupling portion of said conduit means to mechanicallyprevent disconnection of said Well head assembly and said couplingportion of said conduit means, and

controlling the drill pipe passageway of said well head assembly fromsaid support means whereby said drill pipe passageway may be selectivelyclosed ofl? or opened.

References Cited by the Examiner UNITED STATES PATENTS Re. 24,083 8/1948 McNeill 175--7 987,266 3/1911 Smith 1759 2,187,871 1/ 1940'Voorhees 1758 2,512,783 6/1950 Tucker 1758 X 2,684,575 7/1954 Pryor etal. 1758 X 2,808,229 10/1957 Bauer et al 1757 2,891,770 6/1959 Bauer eta1. 175-7 2,923,531 2/1960 Bauer et al 1757 CHARLES E. OCO'NNELL,Primary Examiner.

R. E. FAVREAU, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,315,742 April 25 1967 Kingsley M. Nicolson It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 1, line 48, for "hes" read has column 2, line 72, for "esuipment"read equipment column 3, line 61, for "annual" read annular column 5,line 68, for "vessel 10 to" read vessel 10 column 7, line 49, "cableread cables column 9, line 16, for "hyadrulic" read hydraulic column 12,line 18, for "appaartus" read apparatus column 14, line 7, for "wellassembly" read well head assembly Signed and sealed this 14th day ofNovember 1967.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

1. A METHOD OF PREPARING A WELL IN A FORMATION UNDERWATER FOR WELLWORKING OPERATIONS, SAID METHOD COMPRISING: LOWERING CONDUIT MEANS FROMSUPPORT MEANS DOWNWARDLY THROUGH THE WATER AND POSITIONING SAID CONDUITMEANS AT LEAST PARTIALLY WITHIN AN OPENING EXTENDING DOWNWARDLY INTO ANUNDERWATER FORMATION WITH AN UPPER END OF SAID CONDUIT MEANS SUBMERGEDBENEATH WATER; FROM SAID SUPPORT MEANS, CONVEYING CEMENTITIOUS MATERIALTO A ZONE EXTERIOR OF SAID CONDUIT MEANS AND WITHIN SAID OPENING;SEALINGLY CEMENTING AT LEAST A PORTION OF SAID CONDUIT MEANS TO WALLMEANS OF THE OPENING IN SAID FORMATION; GUIDING A WELL HEAD ASSEMBLYHAVING A WELL APPARATUS PASSAGEWAY EXTENDING THERETHROUGH FROM SAIDSUPPORT MEANS TOWARD SAID CONDUIT MEANS BY LOWERING SAID WELL HEADASSEMBLY IN SLIDABLE ENGAGEMENT WITH FLEXIBLE GUIDE MEANS EXTENDINGDOWNWARDLY FROM SAID SUPPORT MEANS; PRIOR TO SAID GUIDING OF SAID WELLHEAD ASSEMBLY, PROVIDING SAID FLEXIBLE GUIDE MEANS SUPPORTED BY SAIDSUPPORT MEANS AND EXTENDING TO THE GENERAL VICINITY OF SAID SUBMERGEDUPPER END OF SAID CONDUIT MEANS, WITH SAID UPPER END OF SAID CONDUITMEANS BEING EXPOSED; AXIALLY CONVERGING AND ENGAGING PORTIONS OF SAIDWELL HEAD ASSEMBLY AND SAID EXPOSED UPPER END OF SAID CONDUIT MEANS;INTERCONNECTING SAID WELL HEAD ASSEMBLY WITH SAID UPPER END OF SAIDCONDUIT MEANS AND ESTABLISHING SAID WELL APPARATUS PASSAGEWAY IN SEALEDCOMMUNICATION WITH THE INTERIOR OF SAID CONDUIT MEANS; MECHANICALLY ANDDETACHABLY INTERLOCKING SAID INTERCONNECTED WELL HEAD ASSEMBLY AND UPPEREND OF SAID CONDUIT MEANS TO MECHANICALLY P REVENT DISCONNECTION OF SAIDWELL HEAD ASSEMBLY AND SAID UPPER END OF CONDUIT MEANS; MECHANICALLY ANDSELECTIVELY MAINTAINING SAID INTERLOCKING OF SAID WELL HEAD ASSEMBLYWITH SAID UPPER END OF SAID CONDUIT MEANS, WITH SAID INTERLOCKING BEINGSELECTIVELY MAINTAINABLE UNTIL SAID WELL HEAD ASSEMBLY IS TO BEDISCONNECTED FROM SAID END OF SAID CONDUIT MEANS AND RAISED IN SLIDABLEENGAGEMENT WITH SAID FLEXIBLE GUIDE MEANS; AND CONTROLLING THE WELLAPPARATUS PASSAGEWAY OF SAID WELL HEAD ASSEMBLY FROM SAID SUPPORT MEANSWHEREBY SAID WELL APPARATUS PASSAGEWAY MAY BE SELECTIVELY CLOSED OFF OROPENED.